(1) Field of the Invention
The present invention generally relates to a process and apparatus for forming an image on a novel recording medium, and more particularly to a process and apparatus for forming an image on a novel recording medium, the recording medium having a characteristic in which a receding contact angle decreases when the medium is heated in a condition where the medium is in contact with a contact material such as a liquid.
(2) Description of Related Art
An offset printing method using a printing plates without water (water for moisturizing) is a typical one of methods in which a recording medium is divided into areas where it is easy for liquid to adhere thereto and area where it is hard for the liquid to adhere thereto. However, in this offset printing method, it is difficult to incorporate a process for manufacturing printing plates from original plates and a process for printing from the printing plates into a single apparatus. This makes it difficult to have a compact printing apparatus.
For example, even in a case of relatively compact offset printing apparatus, a plate making apparatus and a printing apparatus are separated.
To eliminate this fault of the offset printing method, there has been proposed a recording method and apparatus in which areas where it is easy for the liquid to adhere thereto and areas where it is hard for the liquid to adhere thereto than be formed in accordance with image information and in which the recording medium can be repeatedly used (a process for forming an image is reversible). The following are some of these.
1 Water-soluble developing method
After a charge has been applied from an external device to a hydrophobic photo-electric layer, a medium having the hydrophobic photo-electric layer is exposed so that a pattern having hydrophobic portions and hydrophilic portions is formed on the surface of the hydrophobic photo-electric layer. Then, a water soluble developing solution adheres to only the hydrophilic portions and is transferred to a paper or the like. Such methods and apparatus are disclosed in Japanese Patent Publication Nos. 40-18992, 40-18993 and 44-9512 and Japanese Patent Laid Open Publication No. 63-264392, etc.).
2 Method using a photo-chemical response of a photo-chromic material
In this method, an ultraviolet light is irradiated to a layer which contains a material such as a spiropyran or an azo dye so that a photo-chemical reaction occurs to make the photo-chromic material hydrophilic. Such method and apparatus are described in "Japanese Journal of Polymer Science and Technology" Vol. 37, No. 4 page 287, 1980).
3 Method using an action of an internal biasing forces
In this method, amorphous substances and crystalline substances are formed in a recording medium by a physical transformation, so that portions where it is easy for a liquid ink to adhere thereto and portions where it is hard for the liquid ink to adhere thereto are formed on the recording medium. An example of such is disclosed in Japanese Patent Laid Open Publication No. 54-41902.
According to the previously described method 1, after the water-soluble ink is transferred to the paper or the like, the hydrophilic portions are removed by removing the charge so that it is possible to record other image information. That is, one original plate (photo-electric member) can be repeatedly used for printing images. However, in this method, an electrophotography process is basically used, so that a long time is required for carrying out the process involving steps cf charging, exposing, developing, transferring and discharging. Therefore, it is difficult to make an apparatus compact, to reduce its cost and to make an apparatus in which it is unnecessary to maintain.
In the method 2 described above, it is possible to freely control the reversibility of the hydrophilic and hydrophobic properties by selective irradiation of ultraviolet and visible light. However, since a quantum efficiency is very small, a response time is extremely long and a recording speed is low. In addition, there is also a fault of image instability. Therefore, this method has still not put into practical use.
Furthermore, an information recording member (the recording medium) which is used in the method 3 has stability after an image is formed thereon, but there are occasions structural transformation occurs in the information recording member due to temperature changes prior to the recording. That is, the method 3 has a disadvantage in that it is difficult to maintain the image on the information recording member. In addition, when recorded information patterns is removed, a thermal pulse must apply to the information recording member and then it is necessary to rapidly cool the information recording member. Therefore, it is difficult to perform frequent repetition of image formation.
In a case where ink which is in liquid is used as the recording agent or both the contact material and the recording agent, as the viscosity of the ink is low and the surface of the ink is a free surface, the surface unstably moves when developing. When a plurality dot areas adjacent to each other are developed by the liquid ink, there is a problem in that the ink dots adhered to the dot areas mutually affect each other so that the amount of ink dot adhered to a dot area differs from the amount of ink dot adhered to another dot area. In a case where an apparatus for forming an image by use of the liquid ink is carried, there is a possibility that the ink is slopped out from a container. Thus, it is difficult to handle the apparatus in which the liquid ink is used. In addition, as the liquid ink easily blots on a recording paper, it is difficult to obtain an image having a high quality.